Semiconductor device and manufacturing method thereof

Abstract

One method for manufacturing a semiconductor device includes: forming provisional active regions that are shaped such that active regions that are adjacent in an X direction are connected to each other, forming a sacrificial film, performing etching, including the sacrificial film, so as to form a plurality of first trenches that separate the active regions, embedding element-isolating insulating films in the first trenches and then removing the sacrificial film, forming first side-wall insulating films that cover the exposed side surfaces of the element-isolating insulating films and second side-wall insulating films that cover the side surfaces of the first side-wall insulating films, embedding cap insulating films in second trenches that appear due to the formation of the second side-wall insulating films, and forming a plurality of third trenches at the positions of the second side-wall insulating films and forming word lines thereunder.

What is claimed is: 
     
       1. A semiconductor device comprising:
 a semiconductor substrate; 
 a plurality of first insulating films for element isolation, each of which is embedded in a main surface of the semiconductor substrate and extends in a first direction; 
 a plurality of second insulating films for element isolation, each of which is embedded in the main surface of the semiconductor substrate and extends in a second direction intersecting the first direction, and which, in conjunction with the plurality of first insulating films for element isolation, demarcate a plurality of first active regions disposed in a matrix formation, wherein the plurality of second insulating films extend to a first vertical height relative to the semiconductor substrate; 
 first and second word trenches which are provided extending in the second direction in the main surface of the semiconductor substrate, and which are disposed between two of the plurality of second insulating films for element isolation that are adjacent to one another in the first direction; 
 first and second word lines, embedded respectively in lower portions of the first and second word trenches, with the interposition of gate insulating films; 
 first and second embedded insulating films disposed respectively over first and second word lines, wherein the first and second embedded insulating films extend to a second vertical height relative to the semiconductor substrate, and the second vertical height is greater than the first vertical height; 
 first impurity-diffused layers provided between the first word lines and the second word lines; 
 second impurity-diffused layers provided between the first word lines and one of said two second insulating films for element isolation; and 
 third impurity-diffused layers provided between the second word lines and the other of said two second insulating films for element isolation; 
 wherein the first and second word trenches are formed in self-alignment relative to the plurality of second insulating films for element isolation so that a first width between one second insulating film of the plurality of second insulating films and the first word line trench is substantially equal to a second width between another second insulating film of the plurality of second insulating films and the second word trench. 
 
     
     
       2. The semiconductor device as claimed in  claim 1 , wherein:
 each of the plurality of first insulating films for element isolation is formed from a silicon dioxide film; and 
 each of the plurality of second insulating films for element isolation is formed from a silicon nitride film. 
 
     
     
       3. The semiconductor device as claimed in  claim 1 , comprising:
 bit line contact plugs which are in contact, at their lower surfaces, with the first impurity-diffused layers; and 
 bit lines which are in contact, at their lower surfaces, with the bit line contact plugs. 
 
     
     
       4. The semiconductor device as claimed in  claim 1 , comprising:
 first and second capacitor contact plugs which are respectively in contact, at their lower surfaces, with the second and third impurity-diffused layers; and 
 first and second capacitors which are respectively in contact, at their lower surfaces, with the first and second capacitor contact plugs.